Film drive apparatus



June a, 194s.l

Filed July '4. 1945 M. E. coLLlNs 2,442,400

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Arr-ORNE! Patented June 1, 1948 FILM DRIVE APPARATUS Milford E. Collins, Los Angeles, Calif., assignatto Radio Corporation of America, a corporation A`o! Delaware Application July 4, 1945, Serial No. 603,210

1 claim. (c1. zii-2.a)

This invention relates to sound motion picture iilm apparatus, and particularly to an improved sound recorder drive wherein a simplified iilm path provides a uniform and constant film motion at the translation point where the sound modulated light is impressed on the film.

In the art of sound recording, .particularly on motion picture iilm, many types of nlm drives have been suggested and employed in commercial practice. The primary object of all such lm advancing mechanisms is to provide a uniform and constant iilm motion at the point of light impression. Many systems introduce slow variations in the film speed which produce low frequency wows. This is primarily caused by unbalanced mechanical constructions or designs and lack of damping. Other film advancing mechanisms produce'higher frequency speed variationsy generally caused by short period variations in the lm tension as it comes from the supply reel and is wound on the take-up reel. Certain prior mechanical iilters permit the lm jerks to be transmitted to the translation point. Some film drives, although producing a desirable nlm motion over the recording drum, nevertheless are complicated mechanisms and require continuous inspection and frequent adjustments. Many drives employ soft film loops on both sides of the recording drum which prevent the film from lying iiat against the drum adjacent the sprocket holes.

The present invention is directed to a simple drive with a minimum of operating elements, but which provides a. particularly uniform nlm motion at the translation point. The invention utilizes certain features of prior nlm drives which have provided good film motion, such as a magnetic coupled drive for the lm drum, this invention being shown in Kellogg Patent No. Re. 19,270, of August 14, 1934. 'I'his feature, coupled with a combination feed and drive sprocket in comblination with la simplified form of tensioned guide rollers, provides a short iilm path which is easy to thread and adjust, and which corrects many faults of prior designs. Several forms of drives are described hereinafter, one being shown incorporated in a complete sound recorder, this form having given excellent results because of the features mentioned above.

The principal object of the invention, vtherefore, is to facilitate the recording ofsound on iilrm.

Another object of the invention is to provide an improved film drive for a sound recorder or reproducer.

Aiurther object of the invention is to provide 2 a steady and uniform iilm motion at a light trans` lation point with asimple film path.

A still further object of the invention is to provide a film drive having a minimum of elements between the drive sprocket and the recording drum, while providing maximum illter action to eliminate the introduction of speed irregularities at the translation point and providing a. tight film Wrap over the recording drum.

Although the novel features which are believed to be characteristic of this invention will be pointed out with particularity in the appended claims, the manner of its organization and the mode of its operation will be better understood by referring to the following description read in conjunction with the accompanying drawings forming a par-t hereof, in which:

Fig. 1 is an elevational view of the main section of a sound recorder embodying the invention.

Fig. 2 is a partial section of the drive shown in Fig. 1. Y

Fig. 3 is a partial cross sectional view of one of the guide rollers taken along the line 3-3 of Fig. 2. Y

Fig. 4 is a detail of the guide roller taken along the line 4-4 of Fig. 3.

Fig. 5 is a plan view of the other guide roller shown in Fig. 2, and

Figs. 6 and 'l are diagrammatic views of modications of the lm drive embodying the principles of the invention.

Referring now to Figs. 1-5, inclusive, in which the same numerals identify like elements, a housing 5 with a back plate 6 has mounted thereon a shaft 'l carrying a film sprocket 8 and a chain sprocket Wheel 9, the latter driving a chain I0 for rotating a take-up reel, not shown. Also mounted on the plate 6 is a shaft upon which is mounted a film drum il having a back flange l2. Mountedon the shaft driving the drum Il is a magnetic clutch arrangement, which is disclosed and claimed in the above-identified Kellogg patent, and which is driven by gear I4 from an idler gear I5 which also drives a gear on the shaft 1, the idler gear l5 being driven by a` gear I6 on a shaft having an end bearing shown at I1. Film 2U is shown threaded in the recorder, its direction of advancement being indicated by the arrows. The film path is traced from the left-hand side of sprocket 8 under a pair of pad rollers in an assembly 2|, then under a anged guide roller 23, over the drum Il, around a iianged guide roller 24, and then over the right-hand side of sprocket 8 under a pair of pad rollers in an assembly 26. The pad roller assemblies shown at 2| and 26 are disclosed and claimed in my oopending application, Ser. No. 536,461, filed May 20, 1944, now Patent No. 2,418,544, issued April 8, 1947.

At the top of the casing is an oil reservoir 30, while at the right-hand side of the casing, a footage counter 3l is shown with its train of gears 32. The film passes through an assembly 34 to and from the sprocket 8, this assembly being a punching device. An assembly 35 is a film identifying or marking device, assemblies 34 and 35 being disclosed and claimed in my copending application, Ser. No. 603,209, filed July 4, 1945.

Briefly, the assembly 34 includes a solenoid which operates a punch to perforate the film near its center so that the beginnings and ends of takes may be identified in the dark room. The solenoid also moves a focusing plate 31 against the film to maintain it in a position so that indicia arranged by wheels 38 may be photographed on the film through an optical system 39.

Referring now to Figs. 2-5, inclusive, the film 20 is guided to the single fianged drum II by a double fianged idler roller 23 mounted on an arm 42 having pivot bearing 43. The shaft 44 on which the roller 23 is rotatable, extends beyond the arm 42 as an extension 45 positioned between a U-shaped stop member 41. The bearing 43 is mounted on a shaft 48 fixedly held in the back plate 6. The roller 23 is under tension of a spring 50 attached in a groove of the extension 45 and to a pin 52 fixedly mounted in the plate 6. (See Fig. 4.) To insure that the roller 23 accurately guides the film to the recording drum, provision is made for a longitudinal adjustment of the roller which transversely adjusts the film.

After the roller 23 has been properly aligned with the drum, no further adjustment is required, since the drum II is tapered and thus maintains the film in the proper position thereon. In Fig. 3, the adjusting mechanism for the roller is shown as consisting of a compression spring 54 which bears against the plate 6 and against a flange on a sleeve 55, thus urging the arm 42, and consequently, the roller 23 away from the supporting plate 8. The position of the arm 42 is adjusted and maintained against the spring 54 by means of a split nut 51 having a locking bolt 58 and which is adjustable on the threaded end of the shaft 48.

'I'he take-oli roller 24 is also double flanged and is, similarly mounted on the. plate 6, except that no provision is made for adjusting the roller longitudinally. Roller 26 is mounted on a .shaft 6I having an extension 62 positioned between the U-shaped stop member 63. The shaft 6I is mounted on a bracket arm 65, one end of which is pivoted on a shaft 66 mounted in the plate 6. The U-shaped members 41 and G3 limit the movement of rollers 23 and 24, respectively, thus permitting for variations in the roller positions caused by film with different amounts of shrinkage.

In this film drive, -film is pulled from the supply reel by the sprocket 8, the film passing along the left-hand side thereof. This same sprocket 8 also pulls the film around the drum I I over the idler roller 24', the film being fed to the drum II around the roller 23. It will be noted that both film loops between the sprocket 8 and the drum II are under tension at all times, thus keeping the film tightly wrapped around the drum, which eliminates polygoning of the film at and adjacent to the perforated portion of the film. Low frequency variations are elirriinatedl 4 by the damping action of the magnetic drive. and high frequency variations are eliminated by the tensioning of the film and the filter action of the sprung idler rollers in combination with the magnetic drive.

To thread the recorder, it is only necessary to take the film loop from the magazine, place it around the recording drum II under the guide rollers 23 and 24, and over the sprocket 8. so that the springs 50 and 10 exert tension in the film loops between the sprocket 8 and the drum II. This may be very quickly accomplished in operation, and no further adjustment is required after the guide roller 23 has once been longitudinally adjusted. As mentioned above, the drum I I is tapered with its larger diameter at the flange I2 so that the film will ride adjacent the flange at all times, thus providing accurate edge guiding of the film immediately at the translation point. This simplified form of film drive in which film is tensioned over the recording drum and to a single sprocket which serves as both the feed and drive sprocket, provides very steady film advancement over the drum and prevents external film tension variations from being transmitted to the film while passing over the drum.

Referring now to Fig. 6, a modification of the drive shown in the preceding figures, is illustrated, this modification having a similar drive sprocket 12 and recording drum 18, the film 14, however, passing over an idler sprocket 15 between the drive sprocket 12 and the roller 13 in a manner similar to its passage over sprocket 12. The idler sprocket 15 has its shaft under the ten- 'sion of a spring 16, so that all the film intermediate it and the drum iii is under tension, the sprung sprocket 15 serving as a filter. The sprocket 15 is film pulled.

A third modification is shown in Fig. '1, in which a separate feed sprocket 8D and a separate drive sprocket iii are employed. 'Ihe recording drum is shown at 82. In this modification, separate idler sprockets 94 and 85 are interposed between the drive and feed sprockets and the roller 82, these sprockets being geared together by a pair of gears 31 and 88. The sprocket 84 is mounted on an arm 90 pivoted on the shaft of the sprocket 85 and is under tension of a spring 9|, thus placing tension on the film loops intermediate the sprockets 84 and 85 and the roller 82. Thus, the two modifications shown in Figs. 6 and 7 utilize the same principle which places the film around the recording roller under filter tension provided by a spring and the mass of an idler sprocket or sprockets. Although the drums 18 and 82 may be driven by the above mentioned magnetic drive to provide damping, the drums may be used with solid flywheels, damping being provided by viscous couplings or dash-pots attached to the sprockets 15 and 84, well-known in the art.

I claim:

A sound film apparatus comprising a mounting plate, a sprocket mounted on said plate and adapted to advance film thereover, a recording drum mounted on said plate around which said film is adapted to advance, a first idler roller resiliently 'held against the outer face of said film between said drum and said sprocket, a second idler roller resiliently held against the inner Iface of said film between said drum and said sprocket independently of said first roller, said idler rollers maintaining tension on the film between said drum and said sprocket, whereby high frequency variations in film speed are substan- MRD E. COLLINS.

REFERENCES CITED The followingV references are of record in the me of this ment: A l

UNITED STATES PATENTS Number Name Date Heisler Nov. 10. 1931 Kellogg Feb. 28, 1933 Holman Feb. 15, 1938 ,Victor June 14, 1938 Black May 9, 1939 Woolf Oct. 21, 1941 DeVry et al. Feb. 15, 1942 DeBart. Sr., et al. Jan. 4, 1944 

